Motor vehicle cameras are an essential part of driver assistance systems in modern motor vehicles.
Widespread use is made, for example, of reversing cameras, which can be fitted in the tail end of a motor vehicle. When reverse gear is selected the reversing camera is automatically triggered by a control unit, so that through the interposition of a suitable image processing unit the vehicle environment in the tail area can be shown to the driver on a display in the vehicle interior.
The purpose of such camera systems is frequently to improve road safety by avoiding hazardous situations. By way of example, motor vehicle cameras are used to support automatic distance monitoring systems (ACC=Adaptive Cruise Control), to support safety systems (pre-crash systems, lane assist systems, etc.), and to support parking aids, and the like.
A camera system in a motor vehicle can also be used to increase comfort by relieving the driver of stress and facilitating orientation through environment information conveyed according to the situation or in a way that makes sense to the driver, as for example is the case with assistance systems with traffic sign recognition and/or lane detection or road marking recognition. Such traffic sign recognition or road marking recognition methods typically use a camera to capture the environment alongside or behind the vehicle, evaluate the image data captured and detect in the image data the presence of certain traffic signs or road markings in the actual lane, and possibly those adjacent to it, and the position of the vehicle itself relative to these road markings.
A driver assistance system with a method for detecting road markings is, for example, described in DE 10 2009 048 323 A1.
The core of such camera systems is a suitable optical system. Objectives designed for automotive applications must be designed in such a way that within the relevant temperature range for automotive applications of −40° C. to +95° C. they guarantee the required imaging characteristics. This is especially difficult with objectives which when used as intended are exposed to considerable temperature fluctuations, such as for example cameras arranged behind the windshield, which for example and especially in summer can become very hot, or cameras outside of the vehicle, which in winter can become very cold at extreme temperatures.
For reasons of cost, in present-day camera systems sometimes plastic lenses are preferred to the more expensive and comparatively less resistant glass objectives. The problem here, though, is that the optical characteristics of objectives, such as for example the refractive index, can change according to the temperature. This occurs especially in objectives with plastic lenses, where the optical characteristics are more temperature-sensitive than objectives that use glass lenses.
On top of this, the demands in terms of the optical characteristics of objectives are increasing due to the need for a greater aperture angle and simultaneous longer range in the center of the objective, as in the case with non-linear objectives.
Against this background it is desirable to achieve an improved camera arrangement for motor vehicles. In addition, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.